U.S. Pat. No. 5,670,516 discloses that certain decahydroisoquinoline derivatives are AMPA receptor antagonists, and as such are useful in the treatment of many different conditions, including pain and migraine. In addition, WO 01/02367 A3, published Jan. 11, 2001, discloses diester prodrug forms of the selective GluR5 antagonist 3S,4aR,6S,8aR-6-(((4-carboxy)phenyl)methyl)-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylic acid.
It is an object of the present invention to provide monoesters of (3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylic acid which provide improved bioavailability of the parent monoacid in a patient. In addition, it is an object of the present invention to provide monoesters of (3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylic acid which are substantially converted to the parent monoacid in the patient.